Field of the Invention
The present disclosure relates to image forming apparatuses using electrophotographic processing or the like.
Description of the Related Art
For electrophotographic image forming apparatuses, there is a known configuration in which toner images are sequentially transferred from image forming units of individual colors to an intermediate transfer member, and the toner images are transferred collectively from the intermediate transfer member to a transfer material.
In such image forming apparatuses, each of the image forming units of individual colors includes a drum-shaped photosensitive member serving as an image bearing member. At the time of image formation, toner images developed on the photosensitive members are primarily transferred from the photosensitive members to the intermediate transfer member in a primary transfer portion at which the photosensitive members and the intermediate transfer member are in contact with each other. The toner images of individual colors that are primarily transferred to the intermediate transfer member are secondarily transferred collectively from the intermediate transfer member to a transfer material, such as paper or an overhead projector (OHP) sheet, in a secondary transfer portion in which the intermediate transfer member and a secondary transfer member are in contact with each other and are thereafter fixed onto the transfer material by a fixing unit.
Japanese Patent Laid-Open No. 2004-117722 discloses a configuration in which the surface speed of the intermediate transfer member is set to be higher than the surface speed of the photosensitive member so as to improve the transfer performance of the primary transfer of the toner images from the photosensitive members to the intermediate transfer member. In such a configuration, the primary transfer is performed using a shearing force of shearing the toner images carried by the photosensitive member with the intermediate transfer member.
However, in a so-called cleanerless configuration in which a blade serving as a cleaning member in contact with each photosensitive member is not provided, when the surface speed of the intermediate transfer member is set higher than the surface speed of the photosensitive members, as in Japanese Patent Laid-Open No. 2004-117722, as in Japanese Patent Laid-Open No. 2004-117722, the following problem can occur. That is, in the cleanerless configuration, the load for rotationally driving the photosensitive members is small, so that the photosensitive members are taken along the surface of the intermediate transfer member, causing the positions of the toner images formed on the surface of the photosensitive member to be misaligned to generate image defect.